Spoilers--plot details

I know this is a very old post but nonetheless I felt compelled to reply.

No explanation is given except that the older daughter Radia was once pregnant and her mother "helped her get rid of it" so I can only assume one of the graves was that of her baby. The sisters' father had also "left" according to the younger girl Aicha, "died" according to the older sister Radia so my interpretation is the father of the older girl possibly impregnated her and she and the mother killed him and the baby and buried them. When the younger "disturbed" sister Aicha goes to dig up the baby and show it to the girlfriend Aelma they find instead the skeleton of a dog. Perhaps there really had been a baby buried there at one time but when the mother and older sister found Aicha had discovered it they moved the baby's body and replaced it with a dog? Just guessing at that.

Maybe the younger "sister" Aicha was not really a sister at all but another child of the older sister Radia raised and treated to be her sister rather than her own child since she was not married. That happened a lot in the US when pregnancy of an unmarried woman was so stigmatized in past generations. That would explain the age difference in the "sisters" but that is just something I thought of but no solid reason or explanation is really given in the movie to validate that assumption on my part. This might also explain why the women lived alone in an abandoned house for so long instead of trying to find a place to live in town and interact with society. The stigma of a young woman having a baby out of wedlock and the fact the patriarch of the family is mysteriously "missing" would raise too many questions making it easier to hide out in the abandoned house and survive as best they could. The assumption the younger "sister" is actually the child of the older sister is reinforced when the younger girl is looking at the photo with a visibly pregnant girl who looks a lot like the older sister. When Ali's girlfriend asks is she not in the picture with the others she rubs over the pregnant belly of the older sister as if she knows her "sister" is really her mother.

I don't think it ever states why the people who lived in the main house left but I got that the man Ali was a little boy who once lived there when the older woman was a servant and he had returned with his girlfriend after reaching adulthood(the synopsis states a married couple, but they are clearly *not* married if you follow the conversation the girlfriend has with the older sister while she is bathing her). Early in the movie the mother is shown holding an old photograph of a family with a little boy in the front and she touches his image and says "It is him" when Ali and his girlfriend first arrive at the house.

I re-watched parts of the movie to make sure I didn't misunderstand or miss something as I wanted an explanation as well but it just wasn't there. I suppose we are left to make up our own reasons and explanations as they are not well explained at all by the movie itself. I found a lot of unanswered questions in the movie and storyline itself but I just thought I would share what I personally came up with. I came here to see if someone else had an interpretation of the movie but apparently no one but you has posted so I answered your post.

The other possible explanation is there was no father at all with the mother in the movie and Radia had become impregnated by someone in the family who lived in the large house which could have instigated their moving away to avoid shame coming to their own family. The buried secrets would then be the pregnancy of the daughter of the servant of the house by perhaps the patriarch of that family and the cover up of the birth of the younger girl and hiding her as well as themselves from the rest of the town and society - that would mean there were never any graves at all. I think I covered all the possibilities I could come up with but there was a lot left unexplained in this movie.